CONTACT-PRESSURES. 261 



floret. It would therefore be expected from theoretical construc- 

 tion that the long curves should prove to be stepped, owing to 

 apparent displacement, as the lozenge-shaped flowers readjust to 

 fit into the square meshes of the system.* 



Comparison of fig. 93 shows that such is the case ; the 8-curves 

 are slightly stepped, but the 13-curves run clean-edged. At the 

 apex of the spadix the phyllo taxis system falls normally to (5-f 8), 

 and here again the 8-curves are the smooth ones, while the 

 5-curves are stepped. 



In the case of trimerous flowers, similar secondary relations 

 between the florets produce phyllotaxis effects, which again have 

 little bearing on the primary construction system, in that the 

 trimerous flowers produce a secondary appearance of hexagonal 

 facets which therefore present three lines of contact ; this being 

 again the general case for trimerous Monocotyledonous types 

 (Acorus, Muscari). In dealing with examples of hexagonal facetting 

 it must, however, be clearly borne in mind that hexagonal foMtting 

 has no necessary connection with hexagonal packing. Hexagons 

 which appear very fairly regular may still be orthogonally 

 arranged. By taking a normal orthogonal (8-1-13) system 

 (fig. 95), and cutting off corners at the point of contact, 

 i.e. by pressing the members against each other instead of 

 sliding them, an orthogonal series of hexagons may be obtained, 

 which show a third line of contact according to the mode of 

 operation, 5/8/13 or 8/13/21/; the latter being shown in the 

 figure, which is designed more particularly to illustrate the relation- 

 ship of the prismatic cone scales of P. Pinea. 



* Of. Scliwendener for Displacement Theory, in Goebel's UrganogrwphAj, 

 Eng. trans., p. 80. This does not account for the whole of the phenomena : 

 the adult florets are almost square lozenges (c/. fig. 93), and the greater part of 

 the slip is now due to the radially symmetrical orientation of a decussate (2 + 2) 

 system, individual florets being constructed in median and transverse planes. 

 The effect noticed being thus connected with the subject of the orientation of 

 lateral axes, can with difficulty be included under the heading of Phyllotaxis ; 

 but it is sufficiently clear that though helical curves may intersect to give 

 square facets, it is only when the number of curves in either direction is 

 equal that the diagonals of the facets will be median and transverse planes 

 and no readjustment will be necessary {cf. fig. 110, chap. vi.). 



